Create a property from an intersection of properties

Requires a value to satisfy every member of ..., unlike property_union() which requires at least one. Every member must share the same underlying class since a single value can't be an instance of two different classes at once.

Usage

property_intersection(..., default = NULL)

# S3 method for class 'S7_property'
e1 & e2

Arguments

...

S7 classes or properties to intersect.

default

Any. Passed to S7::new_property().

e1, e2

S7 classes or properties to intersect.

Value

An S7 property whose value must satisfy every member of ....

Examples

library(S7)
PieceColor <- property_intersection(
  property_scalar(S7::class_character),
  S7::new_property(
    S7::class_character,
    validator = function(value) {
      if (!(value %in% c("White", "Black"))) "must be White or Black"
    }
  )
)
Piece := new_class(properties = list(color = PieceColor))
Piece("White")
#> <Piece>
#>  @ color: chr "White"
library(S7)
Piece := new_class(
  properties = list(
    id = property_scalar(S7::class_character) & S7::new_property(S7::class_character)
  )
)
Piece("a")
#> <Piece>
#>  @ id: chr "a"